Question

Find the number of 80V 30microfarad capacitors needed to form a composite capacitor of 400V 30 microFarad

A. 25

B. 40

C. 60

D. 30

Answer 1

Dear student,

capacitors added in series would in crease their voltage capacity but it would reduce their capacitance hence to make a 400V equivalent out of 80V you need to connect 5 capacitors in series.

The effective capasitance will be reduced to
1/(5/30) =30/5 = 6 micro farads

To increase the capacitance to 30 micro farad you need 5 such series lines connected in parallel. (Since the capasitance will get added in parallel connection and the voltage remains same)

That is a total of 5*5 = 25 capacitors are needed.

So the option is a.